Preheat oven to 400 degrees F.
Pierce the outside of the eggplant with a fork 4 or 5 times and cut the eggplant in half lengthwise.
Brush olive oil on the side that was cut.
Place eggplant, cut side down, on a baking sheet coated with cooking spray.
Roast for approximately 30-40 minutes or until skin is crinkly and fork tender.
Remove from oven and allow eggplant to cool for about 10 minutes.
Reduce oven temperature to 350 degrees F.
Scrape flesh into a food processor, discarding outside skin.
Add marinara and salt to food processor and pulse until a chunky consistency.
Scrape eggplant mixture into a baking dish and stir in cheeses.
Bake for approximately 20 minutes or until dip is hot and bubbly.
Garnish with Parmesan cheese and basil, if desired.
Serve hot with crackers, crudites or pita pockets.